The present invention relates to a balancer shaft apparatus for an engine which cancels vibration caused by crankshaft rotation.
In the past, problems associated with engine balancer shafts have been known. For example, the balancer shaft rotates to stir oil in an oil pan, causing the generation of bubbles in the oil or the foaming of the oil, so that the lubricity of the oil is reduced. This stirring also occasionally causes the oil to be splashed into a cylinder block and especially into a crankcase of the engine.
In an effort solve the problem noted above, a variety of proposals have been made. For example, Publication of Japanese Utility Model application No. S62-028937, which is a previous application by the applicant of the present application for patent, discloses a technology in which a balancer shaft is contained in a housing, and a drainage hole is provided on a side wall of the housing for discharging balancer-shaft lubricating oil collected in the housing according to the balancer-shaft rotation.
With the above technology, the stirring and the splashing of the oil in the oil pan caused by the balancer shaft rotation is avoided. In this case, however, another problem arises in that discharged oil in liquid form or in mist form may enter into the cylinder block and especially into the crankcase, consequently, being splashed further by the crankshaft rotation.
The present invention seeks to effectively solve the above mentioned problem, and its object is to provide a balancer shaft apparatus for an engine which efficiently prevents the oil from being stirred in the oil pan during the balancer-shaft rotation and from being splashed into the cylinder block.
To achieve the above object, according to an aspect of the present invention, there is provided a balancer shaft apparatus for an engine, comprising, a bearing beam supporting a crankshaft of the engine and disposed below a cylinder block of the engine, an oil pan for storing lubricating oil for the engine and located below the bearing beam, a balancer shaft housing disposed in the oil pan and containing and rotatably supporting a balancer shaft therein, and a drainage hole formed on the housing and so located above an oil level in the oil pan as to confront the bearing beam, for discharging the oil from the housing into the oil pan during balancer shaft rotation.
Accordingly, oil stir, caused by the discharging of the oil from the housing into the oil pan, is effectively prevented, and oil splash is effectively prevented by the bearing beam as an existing part because the oil is discharged from the housing through the drainage hole located above an oil level in the oil pan during the rotation of the balancer shaft.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments relative to the accompanied drawings.